Biogeochemical Cycle

Yunus Topsakal

Alper Kaan Özgöz

In Earth science, a biogeochemical cycle orsubstance turnover or cycling of substances is apathway by which a chemical substance movesthrough both biotic (biosphere) and abiotic(lithosphere, atmosphere, and hydrosphere)compartments of Earth. A cycle is a series ofchange which comes back to the starting pointand which can be repeated.

The term "biogeochemical" tells us thatbiological, geological and chemical factors are allinvolved. The circulation of chemical nutrientslike carbon, oxygen, nitrogen, phosphorus,calcium, and water through the biological andphysical world are known as biogeochemicalcycles.

IMPORTANT CYCLES

The most well-known and important biogeochemical cycles, for example, include

• the carbon cycle,

• the nitrogen cycle,

• the oxygen cycle,

• the phosphorus cycle,

• the water cycle,

NITROGEN CYCLE

The nitrogen cycle is the process by whichnitrogen is converted between its variouschemical forms. This transformation can becarried out through both biological and physicalprocesses. Important processes in the nitrogencycle include fixation, ammonification,nitrification, and denitrification.

A simple diagram of the nitrogen cycle. The blue boxes represent stores of nitrogen, the green writing is for processes that occur to move the nitrogen from one place to

another and the red writing are all the bacteria involved.

WATER CYCLE

The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly constant over time but the partitioning of the water into the major reservoirs of ice, fresh water, saline water and atmospheric water is variable depending on a wide range of climatic variables.

CARBON CYCLE

The carbon cycle is the biogeochemical cycle

by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Along with the nitrogen cycle and the water cycle, the carbon cycle comprises a sequence of events that are key to making the Earth capable of sustaining life; it describes the movement of carbon as it is recycled and reused throughout the biosphere.

This diagram of the fast carbon cycle shows the movement of carbon between land, atmosphere, and oceans in billions of tons of carbon per year. Yellow numbers are natural fluxes, red are human contributions in billions of tons of carbon per year.

White numbers indicate stored carbon.

OXYGEN CYCLE

The oxygen cycle is the biogeochemical cycle thatdescribes the movement of oxygen within its threemain reservoirs: the atmosphere (air), the totalcontent of biological matter within the biosphere(the global sum of all ecosystems), and thelithosphere (Earth's crust). Failures in the oxygencycle within the hydrosphere (the combined massof water found on, under, and over the surface ofplanet Earth) can result in the development ofhypoxic zones.

PHOSPHORUS CYCLE

The phosphorus cycle is the biogeochemical cyclethat describes the movement of phosphorusthrough the lithosphere, hydrosphere, andbiosphere. Unlike many other biogeochemicalcycles, the atmosphere does not play a significantrole in the movement of phosphorus, becausephosphorus and phosphorus-based compounds areusually solids at the typical ranges of temperatureand pressure found on Earth. The production ofphosphine gas occurs only in specialized, localconditions.

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